America's best cyclist just announced he's not going to the Rio Olympics because of the Zika virus
Zika has mild symptoms in adults but can cause significant birth defects, most famously abnormally small heads, Reuters reports. It is also linked to sometimes fatal neurological syndromes in adults.
Van Garderen's withdrawal from consideration is a blow to Team USA as he is a strong time-trial rider and an equally strong climber.
The 27-year-old twice finished fifth in the Tour de France, in 2012 and 2014. He has won the Tour of California and twice won the USA Pro Challenge, aka the Tour of Colorado.
The Olympic road race will challenge the world's top cyclists on a hilly course that's raced over multiple laps.
While best known as a stage racer, Van Garderen would have found the time trial and the hilly road race to his liking.
USA Cycling will announce the riders selected for Rio on June 24, AP reported.
USA Cycling spokesman Kevin Loughery did not comment when asked how Van Garderen's withdrawal would affect the team's race strategy.
But he told the Associated Press that Van Garderen is the only athlete who has withdrawn from consideration for the US cycling team.
Van Garderen's wife, Jessica, is due in October.
The AP also reported that USA Cycling chief executive Derek Bouchard-Hall said the US Olympic Committee had been taking the lead on educating athletes and "we defer to them" when it comes to preparations. He did acknowledge that South America's first Olympics had been hit by problems.
"I think it has been dogged more than normal and some of the things are beyond their control, and some are not," he told the AP. "For us, it's the velodrome (delays) and some infrastructure problems and the Zika virus, which is not Brazil's fault per se. But they're facing a lot of difficult challenges."
Detroit Tigers closer Francisco Rodriguez has said he contracted the Zika virus over the offseason in his home country of Venezuela and advises potential Olympic athletes to educate themselves about the virus before heading to Rio de Janeiro, the AP reports.
More than 100 health experts have called for the Rio Olympic Games to be postponed or moved because of the threat to public health from Brazil's Zika virus outbreak, according to a public letter published online.